lib/factorial.c


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// Factorial
//
// factorial - n!
//
// n! = 1 * 2 * ... * n, capped at 170!
//
// Inputs:    1 (n)
// Outputs:   1 (n!)
// Constants: 0

#include "ts.h"


ts_parameter_t const ts_factorial_p = { .n_inputs = 1, .n_outputs = 1, .n_constants = 0, .params_size = 0 };


uint_t ts_factorial_offset( ts_constant_t const *c )
{
	( void )c;
	return ( 0 );
}

int ts_factorial(
	fp_t * const *y, uint_t y_n,
	fp_t const * const *x, uint_t x_n,
	uint_t n, ts_constant_t const *c
)
{
	TS_PROLOGUE( ts_factorial_p );
	(void)c;
	for( uint_t i = 0; i < n; ++i )
	{
		if (x[0][i] < 0) { y[0][i] = NAN; continue; }
		fp_t result = 1.0;
		uint_t k = (uint_t)x[0][i];
		if (k > 170) k = 170;
		for( uint_t j = 1; j <= k; ++j )
		{
			result *= (fp_t)j;
		}
		y[0][i] = result;
	}
	return 0;
}